一、引言 物理量间的关系往往在一定的物理规律约束下表示成微分关系式或微分方程。对于某一具体问题的表示形式或解,则可在假定某些条件(如边界条件)成立时,先确定其关系或求得其解。当然,边界条件在有些情况下是很理想的,例如描述电容器充电的暂态过程,可使t=0时,电容器上的电荷q=0,但在另外一些情况下(特别是边界不分明的情况)并不能满足理想的条件,例如水平管中液体流动的情况,不同介质中波传播时界面上波的动作情 I. INTRODUCTION The relations between physical quantities are often expressed as differential relationships or differential equations under the constraints of certain physical laws. For the solution or solution of a specific problem, it may be possible to determine the relationship or obtain the solution if certain conditions (such as boundary conditions) are established. Of course, the boundary conditions are ideal in some cases. For example, to describe the transient process of capacitor charging, the charge q = 0 at t = 0 can be obtained. However, in other cases (especially the boundary is not clear Situation) and can not meet the ideal conditions, such as the level of liquid flow in the tube, the wave propagation in different media when the waves on the interface action